#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int fib(int n)
{
	return n <= 2 ? n : fib(n - 1) + fib(n - 2);
}
int main()
{
	int n = 0;
	scanf("%d", &n);
	printf("%d", fib(n));
	return 0;
}

